1. Technical Field
This invention relates to thermotropic liquid crystalline polyester compositions prepared from 2-methylhydroquinone, hydroquinone, terephthalic acid, and 2,6-naphthalenedicarboxylic acid and characterized as having a high heat distortion temperature (preferably greater than 200.degree. C.) and improved elongation over those identical thermotropic liquid crystalline polyester compositions lacking hydroquinone. This invention further relates to thermotropic liquid crystalline polyester compositions prepared from 2-methylhydroquinone, terephthalic acid, and 2,6-naphthalenedicarboxylic acid, and optionally, hydroquinone, that further contain a reinforcing/filling component selected from the group consisting of glass reinforcing agents, glass fillers, calcium metasilicate, calcium carbonate, titanium dioxide, and calcined aluminum silicate, and that are characterized as having unexpectedly improved elongation in comparison to those identical thermotropic liquid crystalline polyester compositions lacking the reinforcing/filling component. Further, it has been found that the inclusion of carbon fiber into said liquid crystalline polyester compositions prepared from 2-methylhydroquinone, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and optionally, hydroquinone, does not significantly decrease the elongation of said compositions.
The thermotropic liquid crystalline polyester compositions of the present invention can be shaped into fibers, films, or molded articles and are useful in applications where it is desired to use a thermotropic liquid crystalline polyester composition having a high heat distortion temperature and/or improved elongation.
2. Background Art
Liquid crystalline polyesters are described in U.S. Pat. No. 4,118,372. Example 8 of this reference specifically illustrates the preparation of a liquid crystalline polyester from 2-methyl-1,4-phenylene diacetate (i.e., the diacetate of 2-methylhydroquinone), terephthalic acid, and 2,6-naphthalenedicarboxylic acid. However, there is no disclosure in the reference that the elongation of the liquid crystalline polyester composition of Example 8 therein can be improved by preparing said liquid crystalline polyester composition from the same components plus an additional component, i.e., hydroquinone. Further, there is no disclosure in this reference that the addition of a glass filler or glass reinforcing agent, or even other types of fillers or reinforcing agents and other ingredients, to the liquid crystalline polyester composition of Example 8 therein will increase the elongation property of said composition, as is found in the present invention. As such, although U.S. Pat. No. 4,118,372 provides background on liquid crystalline polyester compositions in general, it does not disclose the specific liquid crystalline polyester compositions of the present invention, nor does it disclose the particular advantages possessed by said compositions.
U.S. Pat. No. 4,093,595 discloses a process for polymerizing 2-methylhydroquinone, terephthalic acid, and 2,6-naphthalic acid (also referred to in the art as 2,6-naphthalenedicarboxylic acid) in the presence of a catalytic amount of a compound selected from the group consisting of antimony, tin, and titanium compounds.
Japanese Patent Application Kokai 54-138621 discloses a process for melt spinning a polyarylate which forms an anisotropic melt. Polyarylates comprised of 70 mole percent terephthalic acid, 30 mole percent naphthalene-2,6-dicarboxylic acid (also referred to in the art as 2,6-naphthalenedicarboxylic acid), and 100 mole percent 2-methylhydroquinone are exemplified.
Japanese Patent Application Publication 54-93041 discloses copolyesters of terephthalic acid, naphthalene-2,6-dicarboxylic acid (also referred to in the art as 2,6-naphthalenedicarboxylic acid), and 2-methylhydroquinone.
In none of the preceding references is it disclosed that the particular reinforcing/filling components useful herein may be added to the compositions described therein or that the addition of such a reinforcing/filling component results in an improvement in the elongation property of the compositions.